Q: My iphone 6 doesn't play any game multipalyer....can anyone help me please???

Hey There, Zain779 -

If you are not able to play in multiplayer mode, you may need to change your Game Center settings.  Settings > Game Center > Allow Invites needs to be enabled.  Also, check to make sure you don't have any restrictions enabled that would affect Game Center.  Settings > General > Restrictions

Check out the Game Center section of the iPhone User Guide Below:
https://manuals.info.apple.com/MANUALS/1000/MA1565/en_US/iphone_user_guide.pdf

Using Game Center on your Mac or iOS device - Apple Support
https://support.apple.com/en-us/HT202097​

Cheers,